Preparation method of perovskite film and perovskite pseudo-single crystal thick film

Abstract

The invention provides a preparation method of a perovskite film and a perovskite pseudo-single crystal thick film. The method comprises the following steps: providing a substrate; the method comprises the following steps: mixing a perovskite component and a volatile non-coordination solvent to obtain a perovskite precursor solution; performing a single-layer film manufacturing process for multiple times; the manufacturing process of the single-layer thin film comprises a smearing process, a rotating process and a heating process. In the smearing process, a perovskite precursor solution is smeared on a substrate; a rotation process: rotating the substrate coated with the perovskite precursor solution; and a heating process: heating and pressurizing the substrate coated with the perovskite precursor solution.

Description

Technical Field

[0001] This application relates to the field of perovskite preparation technology, and in particular to a method for preparing a perovskite film and a perovskite quasi-single crystal thick film. Background Technology

[0002] X-ray detection and imaging are widely used in various fields such as medical diagnosis, safety screening, industrial defect detection, and radiation dose assessment. Currently, considering both technological availability and cost, the selection of semiconductor materials for X-ray detection remains limited and involves trade-offs in practical applications. Therefore, there is an urgent need to develop a new type of high-performance, low-cost, and compatible radiation detection semiconductor material for application in X-ray detection and imaging, and many other fields. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this application provides a method for preparing perovskite films and a perovskite quasi-single crystal thick film.

[0004] According to a first aspect of the present application, a method for preparing a perovskite film is provided. The method includes the following steps: providing a substrate; mixing a perovskite component with a volatile non-coordinating solvent to obtain a perovskite precursor solution; and repeatedly performing a single-layer thin film fabrication process. The single-layer thin film fabrication process includes a coating process, a rotation process, and a heating process. Specifically, the coating process involves coating the perovskite precursor solution onto the substrate; the rotation process involves rotating the substrate coated with the perovskite precursor solution; and the heating process involves heating and pressurizing the substrate coated with the perovskite precursor solution. By using a volatile non-coordinating solvent to prepare the perovskite precursor solution and coating it onto the substrate, followed by a rotation and heating process to uniformly distribute the perovskite precursor solution on the substrate while simultaneously evaporating the volatile non-coordinating solvent, the perovskite component crystallizes to form a single-layer perovskite film. Repeating these steps yields a perovskite quasi-single-crystal thick film with adjustable thickness. The rotation process involves rotating the substrate to uniformly distribute the perovskite precursor solution on it. This accelerates the evaporation rate of volatile non-coordinate solvents in the perovskite precursor solution. Increasing the evaporation rate of volatile non-coordinate solvents shortens the time that volatile non-coordinate solvents remain between the lower end of the crystallized perovskite film and the substrate or the upper layer of the perovskite film formed in the previous monolayer film fabrication process. This results in a stronger bond between the newly formed monolayer perovskite film and the substrate or the previous perovskite film, and ensures that the thickness of the formed perovskite film is uniform throughout, thus improving product quality. The heating process promotes the chemical reaction of the perovskite precursor through heating and pressurization, forming a stable perovskite crystal structure. Simultaneously, it removes residual solvents, ensuring the purity and stability of the film.

[0005] Furthermore, the concentration of the perovskite precursor solution is greater than 2 mol / L, and the actual solubility of the perovskite component in the perovskite precursor solution is lower than the saturated solubility of the perovskite component in the volatile non-coordinating solvent at room temperature and pressure. A concentration greater than 2 mol / L ensures that the obtained perovskite film thickness is sufficient to absorb all X-rays, resulting in clearer imaging and more accurate detection results. The fact that the actual solubility of the perovskite component in the perovskite precursor solution is lower than the saturated solubility of the perovskite component in the volatile non-coordinating solvent at room temperature and pressure indicates that the perovskite precursor solution is in a non-supersaturated state, without suspended particles. This allows the perovskite precursor solution to maintain a suitable grain gap between the grains formed during the hot-pressing process, improving the uniformity of the perovskite film thickness and preventing leakage. Simultaneously, reducing the grain gap avoids the need to add non-conductive polymers to reduce porosity, thus preventing the added non-conductive polymers from affecting charge transport.

[0006] Furthermore, the rotation process includes a first stage and a second stage, with the first stage preceding the second stage. The rotation speed in the first stage is lower than the rotation speed in the second stage. A faster rotation speed in the rotation process results in better solvent removal from the perovskite precursor solution. The slower rotation speed in the first stage is to reduce the amount of perovskite components removed along with the solvent, allowing for a thicker perovskite film to be formed. The increased rotation speed in the second stage accelerates the removal of solvent from the perovskite precursor solution, increasing the crystallization rate, accelerating the drying of the perovskite precursor solution, and improving uniformity and adhesion strength.

[0007] Furthermore, the rotation speed in the first stage is 500 rpm; and / or, the rotation speed in the second stage is 1000 rpm. A first stage of 500 rpm and a second stage of 1000 rpm can yield a perovskite film with satisfactory thickness, good uniformity, and high stability.

[0008] Furthermore, in two adjacent single-layer thin film fabrication processes, the rotational speed of the later rotational process is greater than that of the earlier rotational process. Inevitably, uneven crystallization occurs during perovskite film formation. Maintaining a constant rotational speed in the rotational process causes the unevenness to accumulate; that is, in areas with thicker bulges, the solvent in the internal region is more difficult to expel due to its height exceeding the surrounding area. As the solvent evaporates due to this difficulty in expelling, more crystals form at these locations, further increasing the thickness of those areas. This makes it even more difficult for subsequent rotational processes to overcome these areas and form a uniform perovskite film, thus increasing the unevenness of the final perovskite film. By using a higher rotational speed in the later rotational process than in the earlier one, the perovskite precursor solution can obtain greater centrifugal force and higher kinetic energy to overcome the unevenness and form a uniform perovskite film.

[0009] Furthermore, the rotation process includes a first stage and a second stage, with the first stage preceding the second stage; the rotational speed in the first stage is lower than the rotational speed in the second stage. When different rotational speeds exist in a single rotation process, "the later rotational speed is greater than the earlier rotational speed" means that the rotational speed of the later rotational process in the corresponding stage is greater than the rotational speed of the earlier rotational process, that is, the rotational speed of the later first stage is greater than the rotational speed of the earlier first stage, and the rotational speed of the later second stage is greater than the rotational speed of the earlier second stage.

[0010] Furthermore, in the coating process, the perovskite precursor solution completely covers the upper surface of the substrate. Completely covering the substrate during the coating process ensures a uniform thickness of the formed perovskite film.

[0011] Furthermore, the rotation speed of the spin process is 80–2000 rpm; and / or, the time is greater than 100 s. A spin speed greater than 80 rpm can solve the problem of inconsistent edges caused by multiple coatings, while a speed less than 2000 rpm is to prevent the perovskite precursor solution from being too quickly ejected, resulting in a large waste of raw materials. A spin process duration greater than 100 s allows the perovskite precursor solution to be dried as much as possible before entering the heating process to solidify the perovskite.

[0012] Furthermore, the heating process involves a pressure greater than 1 MPa; and / or, a temperature of 80–150°C; and / or, a heating time of 10–30 min. Using a pressure greater than 1 MPa, a temperature of 80–15°C, and a heating time of 10–30 min allows for complete drying of the perovskite precursor solution, and under this environment, the thickness of the formed perovskite film is controllable.

[0013] Furthermore, the single-layer thin film fabrication process is performed at least 10 times. By changing the number of times the single-layer thin film fabrication process is performed, the final thickness of the perovskite film can be controlled, achieving adjustable perovskite film thickness to meet a wider range of needs.

[0014] Further, the perovskite component is ABX3, where A includes one of methylamine, formamidinium, and cesium; B is one of lead or tin; and X is a monovalent halide anion; and / or, the volatile noncoordinating solvent includes one of γ-butyrolactone, acetonitrile, and ethylene glycol methyl ether; and / or, the substrate includes one of glass, silicon wafer, chip, or polyimide; and / or, the grain size in the perovskite film is greater than 20 μm. Using the above configuration, high-quality, large-area perovskite quasi-single-crystal thick films can be obtained.

[0015] According to a second aspect of the present application, a perovskite quasi-single crystal thick film is provided, wherein the perovskite quasi-single crystal thick film is prepared according to the perovskite film preparation method described above.

[0016] The technical solutions provided by the embodiments of this application may include the following beneficial effects:

[0017] In the embodiments of this application, the perovskite film has high crystallinity, uniform orientation, and grain size spanning the entire film thickness. The perovskite quasi-single crystal thick film obtained by the preparation method has advantages such as large manufacturing area, controllable thickness, and universal substrate integration. Its superior carrier transport performance is comparable to that of perovskite single crystal, enabling the integrated X-ray detector to have excellent performance such as extremely low dark current drift, high sensitivity, and low detection limit. It has a wide range of potential applications in multiple fields such as medical diagnosis, industrial inspection, and safety screening.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this application, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] Figure 1 This is a schematic diagram of an X-ray flat panel detector.

[0021] Figure 2 This is a scene diagram of an X-ray flat panel detector during testing.

[0022] Figure 3 This is a schematic flowchart of a method for preparing a perovskite film according to this application.

[0023] Figure 4 This is a surface view of a perovskite quasi-single crystal thick film according to this application.

[0024] Figure 5 The cross-section of the thick film is obtained by scraping with a high-concentration perovskite suspension (6 mol / L).

[0025] Figure 6 The image shows the surface morphology of a thick film obtained by scraping a high-concentration perovskite suspension (6 mol / L).

[0026] Figure 7 This is a surface image of a perovskite film prepared using a low-concentration perovskite suspension.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Common electrode, 2. Interface modification layer, 3. Hole transport layer, 4. Perovskite quasi-single crystal thick film, 5. Electron transport layer, 6. CMOS chip, a. Cross-sectional view, b. Surface view. Detailed Implementation

[0029] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0030] X-ray detection and imaging are now widely used in various fields such as medical diagnosis, safety screening, industrial defect detection, and radiation dose assessment. Currently, considering both technological availability and cost, the selection of semiconductor materials for X-ray detection remains limited and faces trade-offs in practical applications. Halide perovskites, however, have proven promising for X-ray detection and imaging due to their advantages such as high light absorption coefficient, tunable bandgap, high mobility, long carrier recombination lifetime, and strong X-ray absorption. Current research on perovskite X-ray detectors largely focuses on single-device detection and displacement imaging. System-level integration with backend readout application-specific integrated circuits (ASICs), achieving effective electrical connections between large-area perovskite thick films and readout circuits, and realizing high-resolution, high-sensitivity perovskite X-ray detection imaging still faces many challenges.

[0031] To address the aforementioned issues, the inventors developed a perovskite quasi-single crystal thick film 4. X-ray detectors fabricated using this perovskite quasi-single crystal thick film 4 exhibit excellent properties such as extremely low dark current drift, high sensitivity, and low detection limit. They can be integrated into large-size chips to achieve large-area, high-resolution X-ray flat panel detection imaging, and have broad potential applications in multiple fields such as medical diagnosis, industrial inspection, and safety screening.

[0032] like Figures 1-2 As shown, this application provides a perovskite quasi-single-crystal thick film 4, which is used in an X-ray flat panel detector. The back-end readout circuit chip is a complementary metal-oxide-semiconductor (CMOS) or thin-film transistor (TFT), with a pixel size ≤500μm, a pixel array of 64×64, and a pixel area ≤3.2×3.2cm². 2 The X-ray detector with a photodiode-type device structure includes PIN or NIP type. When the X-ray detector is PIN type, it includes a rear-end readout circuit chip 6, an electron transport layer 5, a perovskite quasi-single crystal thick film 4, a hole transport layer 3, an interface modification layer 2, and a common electrode 1 (reference) arranged sequentially along the thickness direction. Figure 1 (As shown). When the X-ray detection is of the NIP type, it includes a rear-end readout circuit chip, a hole transport layer, a perovskite quasi-single crystal thick film, an electron transport layer, an interface modification layer, and a common electrode arranged sequentially along the thickness direction. The electron transport layer is a fullerene derivative C. 60 C 70 Alternatively, a PCBM may be used; the hole transport layer 3 is nickel oxide, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]; the interface modification layer 2 is molybdenum trioxide, cesium carbonate, copper bath, or lithium fluoride; the common electrode 1 is gold or silver; the electron transport layer 5 has a film thickness of 40-200 nm; the hole transport layer 3 has a film thickness of 10-50 nm; the interface modification layer 2 has a film thickness of 4-10 nm; and the common electrode 1 has a film thickness of 50-500 nm.

[0033] In this embodiment, the X-ray flat panel detector, during operation, uses a perovskite quasi-single-crystal thick film 4 to absorb X-rays transmitted through the interface modification layer 2, converting the X-ray energy into electron-hole pairs. The generated electrons and holes are collected onto the detector electrodes by electron transport layers and hole transport layers disposed on both sides of the perovskite quasi-single-crystal thick film, respectively. A CMOS or TFT chip collects the charges and generates current signals. These current signals are amplified and converted into readable X-ray intensity data. By analyzing these signals, X-ray images or intensity information can be obtained. (Reference) Figure 2 As shown, a slotted plate (such as a flat plate) is placed on an X-ray flat plate detector. Figure 2 (As shown on the left), when X-rays irradiate the plate, some of the X-rays pass through slots in the plate to reach the X-ray plate detector, allowing the X-ray plate detector to obtain the corresponding pattern (such as...). Figure 2 (As shown on the right), the pattern is the same as the pattern of the slot.

[0034] Existing perovskite films suffer from several problems: single-crystal structures are difficult to grow in a controllable manner at the centimeter scale using solution methods; large-sized perovskite ingots grown by high-temperature melting methods are difficult to cut and polish using traditional silicon processes; and polycrystalline structures are difficult to fabricate polycrystalline thick films (100 μm). The polymers added to prepare polycrystalline thick films can affect carrier mobility and lifetime, thus affecting the detection performance of the device.

[0035] To address the aforementioned problems, the inventors developed a method for preparing perovskite films. The perovskite films obtained through a single-layer thin-film fabrication process have the advantages of high crystallinity, uniform orientation, and grain size spanning the entire film thickness, thus solving the aforementioned problems.

[0036] like Figure 3 As shown, this application discloses a method for preparing a perovskite film:

[0037] The method for preparing the perovskite film includes the following steps:

[0038] Step 1000: Provide a substrate. Mix the perovskite component with a volatile noncoordinating solvent to obtain a perovskite precursor solution. The perovskite component is ABX3, where A includes one of methylamine, formamidinium, and cesium; B is one of lead or tin; and X is a monovalent halide anion. The perovskite component is an arbitrary mixture of one or more perovskites selected from methylamine lead iodide, methylamine lead bromide, formamidinium lead iodide, formamidinium lead bromide, cesium lead bromide, and cesium lead iodide. The volatile noncoordinating solvent is one or more of γ-butyrolactone, acetonitrile, and ethylene glycol methyl ether.

[0039] Step 2000: Perform the single-layer thin film fabrication process multiple times. The single-layer thin film fabrication process includes a coating process, a spin process, and a heating process. Performing the single-layer thin film fabrication process multiple times allows control over the final perovskite film thickness by varying the number of times the process is performed, thus achieving adjustable perovskite film thickness and meeting more application requirements.

[0040] Step 2100: Coating process, in which the perovskite precursor solution is coated onto the substrate. In this embodiment, during the coating process, the perovskite precursor solution completely covers the upper surface of the substrate, thus ensuring a uniform thickness of the formed perovskite film.

[0041] Step 2200: Spin coating process, in which the substrate coated with the perovskite precursor solution is rotated. This spin coating process addresses the issue of inconsistent edges caused by multiple coatings and prevents excessive spin speed from causing the perovskite precursor solution to be excessively ejected, resulting in significant waste of raw materials. Common non-volatile coordination solvents (DMF, DMSO) can only prepare clear and transparent perovskite precursor solutions with a concentration of approximately 1 mol / L. Spin coating can only yield films with a thickness of less than 500 nm, resulting in small grain sizes (around 100 nm). Furthermore, during spin coating, an anti-solvent needs to be added dropwise for perovskite crystallization to form, and the amount and timing of the added anti-solvent must be precisely controlled; otherwise, it is difficult to form the perovskite crystalline phase.

[0042] Step 2300: Heating process, heating and pressurizing the substrate coated with the perovskite precursor solution. This heating process allows the perovskite precursor solution to be completely dried, and the thickness of the formed perovskite film is controllable.

[0043] Because the blade coating process (i.e., uniformly applying coating material to the substrate surface using a blade or coating knife) requires high substrate flatness, it is not suitable for CMOS chips 6 with readout circuit boards. However, the single-layer thin film fabrication process used in this application is a spin coating process, in which a perovskite precursor solution is applied to the substrate and then spun dry. This process can be adapted to various application scenarios, and the substrates that can be used include, but are not limited to, glass, silicon wafers, chips, or flexible polyimide, such as the TFT chips and CMOS chips 6 mentioned above.

[0044] A perovskite precursor solution is prepared using a volatile non-coordination solvent and coated onto a substrate. Subsequently, a spin-drying and heating process is used to uniformly distribute the perovskite precursor solution on the substrate while simultaneously evaporating the volatile non-coordination solvent. The perovskite components crystallize to form a monolayer perovskite film. Repeating these steps yields a quasi-single-crystal thick perovskite film with adjustable thickness. It should be noted that in this embodiment, the volatile non-coordination solvent refers to a non-coordination solvent with a boiling point below 150°C. It has strong volatility and will evaporate and be ejected during the rotation process. The rotation process involves rotating the substrate to drive the uniform distribution of the perovskite precursor solution on the substrate, which accelerates the evaporation rate of the volatile non-coordination solvent in the perovskite precursor solution. Increasing the evaporation rate of the volatile non-coordination solvent can shorten the time that the volatile non-coordination solvent remains between the lower end of the crystallized perovskite film and the substrate or the upper layer of the perovskite film formed in the previous monolayer film fabrication process. This makes the newly formed monolayer perovskite film more firmly fixed to the substrate or the previous layer of perovskite film, and makes the thickness of the formed perovskite film uniform throughout, thus improving product quality. The heating process promotes the solidification of perovskite through heating and pressurization, forming a stable perovskite crystal structure, while removing residual solvents to ensure the purity and stability of the film. It should be noted that the substrate provided in the first single-layer thin film fabrication process is the substrate itself, while the substrate in the second and subsequent single-layer thin film fabrication processes is a combination of the substrate, the perovskite film formed before the current single-layer thin film fabrication process, and the initially provided substrate.

[0045] The inventors discovered in practice that when the concentration of the perovskite suspension is too high (e.g., 6 mol / L), it affects the cross-sectional and surface morphology of the thick film obtained by scraping (see reference). Figure 5 and Figure 6 (as shown) and surface diagrams of perovskite quasi-single crystal thick films (reference) Figure 4 As shown in the figure, a comparison reveals that when the concentration of the perovskite suspension is too high, the perovskite film obtained by the single-layer thin film fabrication process has many pores, small grains, and uneven size. When the concentration of the perovskite suspension is too high and reaches a supersaturated state, it will precipitate too quickly during the spin process due to the supersaturated state, making it impossible to form a perovskite film of uniform thickness. Figure 7 This is a surface image of a perovskite film prepared using a low-concentration perovskite suspension, compared with... Figure 4 and Figure 7 It is known that when the concentration of the perovskite precursor solution is too low, a perovskite film of sufficient thickness cannot be formed, resulting in poor X-ray absorption. Furthermore, the formed perovskite film has a small grain size and numerous grain boundary interstices, leading to the introduction of more grain boundary defects, reducing charge extraction efficiency, and affecting the detection sensitivity of the device. However, the perovskite suspension used in this application has a concentration of 2-4 mol / L, resulting in a perovskite film such as… Figure 4 As shown, the surface is flat, the grain size is large, the grain boundary gaps are few, and it is less likely to have grain boundary defects.

[0046] Through extensive experimentation, the inventors discovered that a perovskite suspension concentration of 2-4 mol / L is optimal, yielding perovskite films with high crystallinity, uniform orientation, and grain sizes spanning the entire film thickness. When the concentration of the perovskite precursor solution is greater than 2 mol / L, the resulting perovskite film thickness is sufficient to absorb all radiation, resulting in clearer imaging and more accurate detection results. When the concentration of the perovskite precursor solution is less than 4 mol / L, the resulting perovskite film has fewer pores and a smoother surface, with large and uniform grain sizes, exhibiting good X-ray absorption capabilities. The actual solubility of the perovskite component in the perovskite precursor solution is lower than the saturated solubility of the perovskite component in a volatile non-coordinate solvent at room temperature and pressure. This indicates that the perovskite precursor solution is in a non-supersaturated state, without suspended particles. Furthermore, the perovskite precursor solution has a high concentration and is clear and transparent. This allows for suitable grain spacing between the grains formed during the hot-pressing process, improving the uniformity of the perovskite film thickness and preventing leakage. Simultaneously, by reducing the grain spacing, the addition of non-conductive polymers to reduce porosity is avoided, thereby improving the charge transport efficiency and conductivity of the perovskite film. In practical applications, the perovskite quasi-single-crystal thick film 4 is often used in X-ray detectors. Its upper and lower surfaces are connected to semiconductor materials. After absorbing X-rays, it generates separated free electrons and holes, forming a current. Avoiding the addition of non-conductive polymers improves conductivity and enhances performance.

[0047] In this embodiment, the rotation process includes a first stage and a second stage, with the first stage preceding the second stage. The rotation speed in the first stage is lower than that in the second stage. Extensive experiments have shown that a faster rotation speed in the rotation process improves the solvent removal from the perovskite precursor solution, but leads to an increase in the amount of perovskite component removed along with the solvent. Conversely, a slower rotation speed improves the utilization efficiency of the perovskite component and increases the total amount of perovskite film formed, but increases the rotation process time, reducing preparation efficiency and decreasing the adhesion strength between the newly formed perovskite film and its underlying substrate structure due to reduced solvent drying efficiency. The slower rotation speed in the first stage is to reduce the amount of perovskite component removed along with the solvent, resulting in a thicker perovskite film formed in a single pass. The increased rotation speed in the second stage accelerates the removal of solvent from the perovskite precursor solution, increases the crystallization rate, speeds up the drying of the perovskite precursor solution, improves the uniformity of the perovskite film thickness, and simultaneously increases the adhesion strength between the perovskite film and its underlying substrate structure.

[0048] Furthermore, in step 2100 of the coating process, the perovskite precursor solution completely covers the upper surface of the substrate. Completely covering the substrate during the coating process ensures a uniform thickness of the formed perovskite film. The first coating completely covers the upper surface of the substrate and is in direct contact with it. Subsequent coatings completely cover the upper surface of the perovskite film formed in the previous single-layer film fabrication process and are in direct contact with it. Of course, this can also be understood as completely covering the upper surface of the substrate.

[0049] Regarding the rotation process in step 2200, the inventors conducted the following research:

[0050] The rotation speed of the process is 80–2000 rpm, and the duration is greater than 100 seconds. A rotation speed greater than 80 rpm can solve the problem of inconsistent edges caused by multiple coatings, while a speed less than 2000 rpm is to prevent the perovskite precursor solution from being too quickly ejected, resulting in a large waste of raw materials. A rotation duration of more than 100 seconds allows the perovskite precursor solution to be dried as much as possible before entering the heating process to solidify the perovskite.

[0051] In this embodiment, the rotation speed in the first stage is 500 rpm, and the rotation speed in the second stage is 1000 rpm. Using the rotation speeds described above for both stages allows for the acquisition of a perovskite film with satisfactory thickness, good uniformity, and high stability. Rapid spin coating promotes the rapid expansion and solidification of the perovskite precursor solution, which is beneficial for larger crystal sizes and more uniform distribution. This helps reduce crystal defects and improve crystallinity, thereby improving the photoelectric properties of the film. Furthermore, by adjusting the rotation speed, the solution distribution and the final thickness of the film can be more precisely controlled with each application. Rapid rotation helps form a more uniform and dense perovskite film, reducing performance fluctuations caused by thickness inhomogeneity. Moreover, the faster spin coating speed reduces the time for each spin coating process, thereby improving the efficiency of the entire preparation process. In addition, rapid spin coating produces a more uniform surface, reducing surface defects and inhomogeneities, thereby improving the optical transmittance and charge transport efficiency of the perovskite film. Of course, in other embodiments, only the rotation speed in the first stage can be guaranteed to be 500 rpm to ensure that excessive perovskite components are not wasted during the first stage of the spin coating process. Alternatively, the rotation speed in the second stage can be kept at 1000 rpm to ensure rapid expansion and solidification of the perovskite precursor solution, which is beneficial for larger crystal size and more uniform distribution.

[0052] Furthermore, in this embodiment, in two adjacent single-layer thin film fabrication processes, the rotation speed of the later rotation process is greater than that of the earlier rotation process. Inevitably, uneven crystallization occurs during perovskite film formation. Maintaining a constant rotation speed in the rotation process causes unevenness to accumulate, meaning that areas with thicker protrusions are more difficult to expel solvent from their interior regions due to their height exceeding the surrounding area. As the solvent evaporates due to this difficulty in expelling it, more crystals form at those locations, further increasing the thickness and making it even more difficult for subsequent rotation processes to overcome these areas and form a uniform perovskite film, thus increasing the unevenness of the final perovskite film. By using a higher rotation speed in the later rotation process than in the earlier one, the perovskite precursor solution can obtain greater centrifugal force and higher kinetic energy to overcome the unevenness and form a uniform perovskite film.

[0053] Furthermore, the rotation process includes a first stage and a second stage, with the first stage preceding the second stage; the rotational speed in the first stage is less than the rotational speed in the second stage. In two adjacent single-layer thin film fabrication processes, the rotational speed in the first stage of the first process is referred to as v1, and the rotational speed in the second stage as v2. Similarly, the rotational speed in the first stage of the second process is referred to as v3, and the rotational speed in the second stage as v4. When different rotational speeds exist in a single rotation process, "the later rotational speed is greater than the earlier rotational speed" means that the rotational speed of the later rotational process in the corresponding stage is greater than the rotational speed of the earlier rotational process, i.e., v3 > v1, and v4 > v2. It should be noted that in this embodiment, "the later rotational speed is greater than the earlier rotational speed" means that the rotational speed of the later rotational process in the corresponding stage is greater than the rotational speed of the earlier rotational process, i.e., v3 > v1 and v4 > v2, but it does not necessarily mean that v3 > v2. However, in other embodiments, it can be based on v3>v1 and v4>v2, where v3>v2, that is, for two adjacent single-layer thin film fabrication processes, v4>v3>v2>v1; or it can be based on v3>v1 and v4>v2, where v3>v2. <v2。

[0054] In addition, the end time of the rotation process is mainly determined by the color of the perovskite film. When the perovskite film changes completely from a yellow liquid to a black solid, the current rotation process can be ended and the heating process can begin.

[0055] Regarding the heating process in step 2300, the inventors conducted the following research:

[0056] In this embodiment, the heating process uses a pressure greater than 1 MPa, a temperature of 80–150°C, and a duration of 10–30 min. Using a pressure greater than 1 MPa, a temperature of 80–150°C, and a heating time of 10–30 min ensures complete drying of the perovskite precursor solution, and the thickness of the formed perovskite film is controllable under these conditions. Specifically, a heating temperature greater than 80°C ensures complete evaporation of any remaining solvent in the perovskite precursor solution, reducing residue, while a heating temperature less than 150°C saves energy and protects the perovskite film from deterioration. Using a heating pressure greater than 1 MPa allows the resulting perovskite film to better undergo a self-healing process, resulting in a smooth surface on the final quasi-single-crystal thick perovskite film, improving the accuracy of detection results. The duration of the heating process determines the effectiveness of the perovskite film's self-healing; the heating process can be terminated after a predetermined time, such as 30 min.

[0057] In this embodiment, the single-layer thin film fabrication process is performed at least 10 times. By changing the number of times the single-layer thin film fabrication process is performed, the final thickness of the perovskite film is controlled, achieving adjustable perovskite film thickness to meet a wider range of requirements. The grain size in the perovskite film is greater than 20 μm, meaning the thickness of the perovskite film is 200 μm.

[0058] In this embodiment, the perovskite film prepared by the single-layer thin film fabrication process is the same as the perovskite quasi-single crystal thick film used in the application.

[0059] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0060] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a perovskite film, characterized in that, Includes the following steps: Provide substrate; The perovskite component and a volatile noncoordinating solvent were mixed to obtain a perovskite precursor solution. The single-layer film fabrication process is performed multiple times; the single-layer film fabrication process includes coating, spinning, and heating processes. The coating process involves coating the perovskite precursor solution onto a substrate. A spin process is used to spin a substrate coated with the perovskite precursor solution. The heating process involves heating and pressurizing the substrate coated with the perovskite precursor solution.

2. The method for preparing a perovskite film according to claim 1, characterized in that: The concentration of the perovskite precursor solution is greater than 2 mol / L, and the actual solubility of the perovskite component in the perovskite precursor solution is lower than the saturated solubility of the perovskite component in the volatile noncoordinating solvent at room temperature and pressure.

3. The method for preparing a perovskite film according to claim 1, characterized in that: The rotation process includes a first stage and a second stage, with the first stage preceding the second stage; The rotational speed in the first stage of the rotary process is lower than the rotational speed in the second stage.

4. The method for preparing a perovskite film according to claim 3, characterized in that: The rotational speed in the first stage is 500 rpm; and / or, the rotational speed in the second stage is 1000 rpm.

5. The method for preparing a perovskite film according to claim 1, characterized in that: In two consecutive single-layer thin film fabrication processes, the rotation speed of the latter rotation process is greater than that of the former rotation process.

6. The method for preparing a perovskite film according to claim 1, characterized in that... ； The rotation process includes a first stage and a second stage, with the first stage preceding the second stage; The rotational speed in the first stage of the rotary process is lower than the rotational speed in the second stage.

7. The method for preparing a perovskite film according to claim 1, characterized in that: In the coating process, the perovskite precursor solution completely covers the upper surface of the substrate.

8. The method for preparing a perovskite film according to claim 1, characterized in that: The rotation speed of the rotary process is 80 to 2000 rpm; and / or the time is greater than 100 s.

9. The method for preparing a perovskite film according to claim 1, characterized in that: The heating process is performed at a pressure greater than 1 MPa; and / or at a temperature of 80–150 °C; and / or for a duration of 10–30 min.

10. The method for preparing a perovskite film according to claim 1, characterized in that: The single-layer thin film manufacturing process is performed 10 times or more.

11. The method for preparing a perovskite film according to claim 1, characterized in that: The perovskite component is ABX3, where A includes one of methylamine, formamidinium, and cesium; B is one of lead or tin; and X is a monovalent halide anion; and / or, The volatile noncohesive solvent includes one of γ-butyrolactone, acetonitrile, and ethylene glycol methyl ether; and / or, The substrate comprises one of glass, silicon wafer, chip, or polyimide; and / or, The grain size in the perovskite film is greater than 20 μm.

12. A perovskite quasi-single crystal thick film, characterized in that: The perovskite quasi-single crystal thick film is prepared by the method for preparing perovskite films according to any one of claims 1-11.

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